On Sun, 2006-07-09 at 12:38 -0500, Roy Koeppe wrote:
> "How hard is everyone driving the ALC? Driving ALC hard on CW will
> shorten the output rise time. And some suggest that CW driving the AC
> hard can lead to oscillations in the envelope right where the rise to
> ALC? I don't use no stinkin' ALC!
> 73, Roy K6XK
> Are you driving a final either in the radio or external? Are you not
> using ALC? Then how are you preventing that PA from being driven to
> clipping and creating clicks from that clipping?
> We're discussing Orion here, in CW mode. Orion has no ALC input jack and
> no ALC adjustment control for CW transmission. It has an accurate RF
> output level adjustment which you set for proper drive to your
> amplifier, so you never over-drive it. I own three amps, which I set for
> the tubes' plate current maximum ratings, or less. They are far from
> ever being over-driven and are properly loaded at the power used at the
> Haven't you seen an Orion? :-)
> 73, Roy K6XK
No, I've not seen an Orion. But having an RF output level adjustment to
me says it may well have an ALC function in the software and hardware.
Its been the best solution to controlling output power by sampling that
output power and setting the gain to limit that output power. When the
signal off gain rises (due to ALC decay) then the gain is too high on
the next key closing and there's a chance for an ALC induced click as it
controls the output power and with ALC limiting the power it limits
before the full rise time of the drive has occurred and so shortens the
As a practical matter the analogue circuit gain varies too much with
load, temperature, and frequency to not use an ALC type feedback loop to
control the output. Anything else is not going to be accurate. Setting
time constant for the ALC is always a problem.
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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